Open your mouth like short o, then push your lips forward into a round shape and hold it — aww, as in 'all' and 'saw'.
Check yourself: Mirror: wide open AND round lips at the same time. Short o is open with flat lips; this one is open with round lips.
Watch for: Short o. In much of American English 'cot' and 'caught' are the same word — do not fight your own accent. Teach the spelling and accept the vowel your class actually says.
◆ marks a word that does NOT follow today's pattern — Blumenfeld boxes these on the page. Teach it by heart; do not let the class sound it out and lose faith in the rule.
Say the word, have them repeat it, count the sounds on fingers, THEN write. The count is what stops a child writing the first letter and guessing the rest.